如何解决System.Linq.Dynamic.Core-错误消息:“目标对象不是ExpandoObject”
当对集合(在下面的示例中为“数据”类型)执行GroupBy时,当我尝试转换为列表时,消息“目标对象不是ExpandoObject”会发生运行时错误。错误是什么意思?我该如何传递这个错误?
data.AsQueryable()。GroupBy(groupingKeySelector,“ it”)。Select(选择器.Cast()。ToDynamicList()
下面提供的代码详细信息-
//data object is a list of defined class 'Data'.
public class Data {
public string Currency { get; set; }
public int PreTaxCost { get; set; }
}
//variable values:
var groupingKeySelector = "new (it.Currency as Currency )"
var selector = "new ( Sum(Convert.ToInt32(it.PreTaxCost)) as PreTaxCost,it.Key.Currency )"
//Call that throws exception: data.AsQueryable().GroupBy(groupingKeySelector,"it").Select(selector).Cast().ToDynamicList()
//Variation of call that throws same exception data.AsQueryable().GroupBy("new (it.Currency as Currency )","it").First()
异常消息
data.AsQueryable()。GroupBy(groupingKeySelector,“ it”)。Select(selector).Cast()。ToDynamicList()'引发了类型为'system.invalidOperationException'的异常数据:{System.Collections.ListDictionaryInternal} HResult:-2146233079 HelpLink:null InnerException:null消息:“目标对象不是ExpandoObject”源:“ System.Linq.Dynamic.Core” StackTrace:“位于System.Linq.Dynamic.Core.Dynamic.DynamicIndex(对象obj,字符串名称)在C:\ Users \ Jonathan \ Documents \ GitHub \ System.Linq.Dynamic.Core \ src \ System.Linq.Dynamic.Core \ Dynamic \ DynamicIndexer.cs:行30 \ r \ n在lambda_method(Closure, System.Linq.Lookup2.Create [TSource]上的对象)\ r \ n(System.Linq.GroupedEnumerable3.GetEnumerator()\ r \ n在System.Linq.GroupedEnumerable3.GetEnumerator()\ r \ n在System.Linq.Lookup2.Create [TSource](IEnumerable1源,Func2 keySelector,Func2 elementSelector,IEqualityComparer1比较器)\ r \ n .Linq.Enumerable.WhereSelectEnumerableIterator2.MoveNext()\ r \ n在System.Collections.Generic.List1..ctor(IEnumerable1 collection)\ r \ n在System.Linq.Enumerable.ToList [TSource](IEnumerable1源)\ r \ n位于C:\ Users \ Jonathan \ Documents \ GitHub \ System.Linq.Dynamic.Core \ src \ System.Linq.Dynamic中的System.Linq.Dynamic.Core.DynamicEnumerableExtensions.ToDynamicList(IEnumerable源)。 Core \ DynamicEnumerableExtensions.cs:line 87“ TargetSite:{System.Object DynamicIndex(System.Object,System.String)}
解决方法
您确定您的代码给出了错误,因为在LinqPad中运行此代码时:
public class Data
{
public string Currency { get; set; }
public int PreTaxCost { get; set; }
}
void Main()
{
var groupingKeySelector = "new (it.Currency as Currency )";
var selector = "new ( Sum(Convert.ToInt32(it.PreTaxCost)) as PreTaxCost,it.Key.Currency )";
var data = new[]
{
new Data { Currency = "$",PreTaxCost = 5 },new Data { Currency = "$",PreTaxCost = 10 },new Data { Currency = "EURO",PreTaxCost = 20 },};
var result = data.AsQueryable().GroupBy(groupingKeySelector,"it").Select(selector).ToDynamicList();
result.Dump();
}
结果如下:
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